Chapter 18 Flashcards
What are the two components of the mitochondria?
1) the inner membrane space between the outer and the inner membranes
2) the matrix, which bounded by the inner membrane
Where does oxidative phosphorylation take place?
in the inner mitochondrial membrane
T/F The inner membrane is permeable to nearly all ions and polar molecules.
False
What is oxidative phosphorylation?
the electron-transfer potential of NADH or FADH2 is converted into the phosphoryl-transfer potential potential of ATP.
T/F
A strong reducing agent (such as NADH) is poised to donate electrons and have a negative reduction potential.
True
T/F
A strong oxidizing agent (such as O2) is ready to accept electrons and has a positive reduction potential.
True
What is driving force of the electron transport chain?
the electron transfer potential of NADH and FADH2 relative to that of O2
The released energy from the reduction of O2 with NADH generates a _________ that is used for the synthesis of ATP and the transport of metabolites across the mitochondrial membrane.
proton gradient
__________ within the transmembrane complexes leads to the transport of protons across the inner mitochondrial membrane.
Electron flow
__________ is special electron carrier that shuttles electrons from Complex I to Complex II.
Ubiquinone (Q)
Where do the electrons of NADH enter the ETC?
Complex I
How do electrons from NADH enter the ETC?
the initial step is the binding of NADH and the transfer of its electrons to FMN. Electrons are then transferred to series of Fe-S clusters and then passed on to Q
T/F
When accepting two electrons, Q takes up two protons from the matrix as it is reduced to QH2.
True
How do electrons from FADH2 enter the ETC?
electrons from FADH2 are transferred to Fe-S centers of Complex II and then to Q for entry into the ETC
(electrons can also be transferred through glycerol phosphate dehydrogenase)
What is the function of Q-cytochrome c oxidoreductase (Complex III)?
to catalyze the transfer of electrons from QH2 to oxidized cytochrome c, a water-soluble protein, and concomitantly pump protons out of the mitochondrial matrix (2H+ to the cytoplasmic side)
What is a cytochrome?
an electron-transferring protein that contains a heme group
T/F
The iron ion of a cytochrome alternates between a reduced ferrous (+2) state and an oxidized ferric (+3) state during electron transport.
True
How does Complex III accept electrons?
In addition to hemes, the enzyme contains an iron-sulfur protein with an 2Fe-2S center. This coordination stabilizes the center in its reduced form, raising its reduction potential so that it can readily accept electrons from QH2
How does the Q cycle work?
Two QH2 molecules bind to the complex consecutively, each giving up two electrons and two H+. These protons are released to the cytoplasmic side of the membrane. One electron flows to a molecule of oxidized cyto c converting it to the reduced form. The second passes through the two heme groups of cyto b to an oxidized Q and reduces it to a semiquinone radical anion.
T/F4
On the addition of the second electron, the Q radical takes up two H+ from the matrix side. The removal of these two protons from the matrix contributes to the formation of the proton gradient.
True
How many protons are released to cytoplasmic side and how many protons are removed from the mitochondrial matrix in the Q cycle??
4
What does cytochrome c oxidase (Complex IV) do?
catalyze the transfer of electrons from the reduced form of cytochrome c to molecular oxygen
How many electrons are funneled to O2 to completely reduce it to H2O?
4
T/F
The copper centers of Complex IV alternate between Cu+ and Cu2+ as they accept and donate electrons.
True